1. Double Ventricular Response to an Extrastimulus in a Patient with Triple Atrioventricular Pathways 
Joao Pimenta, M.D., Manoel Miranda, M.D., Lélio A. Silva, M.D. 
CHEST 
Volume 74, Issue 5, Pages (November 1978)
DOI: /chest
Copyright © 1978 The American College of Chest Physicians Terms and Conditions

2. Figure 1
Tracings obtained with leads 2 and V1, high right atrium (RA), and His bundle electrogram (HBE), recorded simultaneously. Vertical lines indicate one second. A (top), During sinus rhythm and atrial pacing with rate slightly higher than sinus rate, there is prolongation of A-H interval, with His bundle potential (H) falling on ventricular complexes. First H (at left) can be seen at onset of ventricular depolarization (within delta wave), but two complexes at right show His activation within ventricular depolarization. B (middle), A1-A2 interval of 330 msec, with H2 shortly after V2 (arrow). C (bottom), At A1-A2 interval of 310 msec, H2 is clearly seen after V2, on both occasions due to lengthening of A2-H2 interval.
CHEST  , DOI: ( /chest )
Copyright © 1978 The American College of Chest Physicians Terms and Conditions

3. Figure 2
Tracings obtained with leads 2 and V1, high right atrium (RA), and His bundle electrogram (HBE), recorded simultaneously. A (top), At coupling interval of 300 msec, A2-H2 interval is 200 msec, with H2 after V2. B (middle), At A1-A2 interval of 295 msec, there is double ventricular response (V2 along anomalous pathway and V3 along normal atrioventricular pathway, with normal intraventricular conduction), with sudden increase in A2-H2 interval, reaching 350 msec. C (bottom), By shortening coupling interval (A1-A2 interval of 260 msec), A2-H2 interval becomes shorter (250 msec), and ventricular activation (Vs) shows left bundle-branch block.
CHEST  , DOI: ( /chest )
Copyright © 1978 The American College of Chest Physicians Terms and Conditions